This black thread is used to create sutures on cloth spheremaps. When it is used in this way, spheres not directly connected by an intervening set of gates can be sutured together so that one can reach from one sphere to the next through a single Spherewalk. The formerly intervening gates and spheres disappear from the multiverse; each sphere so lost enters its own pocket universe.
The thread folds the fabric of the multiverse, bypassing some gates and spheres, and linking others directly for the first time. In doing so, it creates discontinuities and ripples over a broad area of the multiverse spanning multiple spheres. These distortions can alter the Fate of a sphere. Rather than the Fate of a sphere being represented by the tension between the opposite poles of a single card in the Fortune Deck, the spheres effected by this thread may find that their Fates bring one card of the Fortune Deck into tension with another. This can lead to implosions.
So where did this thread come from? Is it the hair of some god or dragon? Some wild beast? Or is it hair drawn down from the Crown of Night herself, each strand a fate, each stitch a doom?